Cistern



R. E. DILL NOV. 24, 1925.

CISTERN Filed March 12. 1923 i f r: l

EICHAFED E. DILL. INVENTOR.

" [ATTORNEY Patented Nov. 24, 1925.

UNITED STATES RICHARD E. DILL, OF ALEXANDRIA, NEBRASKA.

CISTERN.

Application filed. March 12, 1923. Serial No. 624,449.

To all whom it may concern.

Be it known that I, RICHARD E. DiLL, a citizen of the United States,residing at Alexandria, in the county of Thayer and State of Nebraska,have invented certain new and useful Improvements in Cisterns, of whichthe following is a specification.

My invention relates to cisterns, and it has particular reference to acistern which is specially adapted for use on farms and suburban placesto furnish a constant supply of water for the home and for the barnyard.

Certain conditions affecting water supply systems are common to a largeportion of the entire Mississippi V alley, and these conditions must beconsidered in designing a successful system of this kind. Nearly allfarms and suburban homes in the middle west include one or morewindmills as a part of their equipment. While the farm is largelydependent on the windmill for the power for raising the water, thispower fluctuates and frequently does not function for short periods withthe result that the owner must pump the water by hand or must use anengine until the wind blows again. This condition has resulted in theinstallation of many pressure tanks of various kinds, probably the mostpopular of which has been the steel tank.

The steel tank has not been altogether satisfactory owing to its highinitial cost, its short life, and its tendency to rust and to thus taintthe water. It has long been recognized that the underground pressurecistern made of concrete would be the ideal cistern, but the high costof cast concrete and the tendency of the concrete to check and crack andto thus release the pressure have combined to discourage the use ofconcrete for this purpose.

A climatological factor of the middle west which affects the success ofthe underground cistern is the range of ten'iperatures between wideextremes. Such temperatures may vary in a single year between fortydegrees below zero to a hundred and ten degrees above. During periods ofextreme heat the water in storage may be so warm as to be unfit fordrinking purposes, but when the opposite extreme is reached the systemis apt to cease functioning or even to burst because of the freezing ofthe water. In the ideal system the water would of course have a fairlyconstant temperature regardless of variations in the outsidetemperatures.

Among the objects of my invention is an improved cistern and the methodof constructing it are low cost of construction and installation,durability, and resistance to destructive chemical and climatologicalaction. The cistern its designed for the storage of water at fairly eventemperatures throughout the year, the water being aerated by the airunder pressure, and the water being delivered to the faucet undersubstantially constant pressures.

Having in view these objects and others which will appear in thedescription, I will now refer to the drawings, in which The figure showsa median vertical sec tional view of my cistern and of a portion of thewell pit.

The structure of my cistern can, at least partly, be best explained byreference to the method of constructing it. I first excavate arelatively deep cylindrical hole in the desired location, the holehaving a relatively small diameter. In general the subsoil into whichthe hole is cut is a stiff, heavy, and tenacious clay which increases intenacity with increase in depth. I plaster the floor and walls of theexcavation with a concrete plaster, in some instances mixing therewith asmall proportion of lime plaster. I then build the forms for casting theconcrete partition and roof, positioning all of the necessary pipes andconnections in the forms before pouring the concrete. The advantages ofthe plastered walls combined with the cast partition and roof will befully explained in the subsequent description.

The space enclosed by the walls 10, the floor 11, and the roof 12 isdivided by the partition 18 into an upper water chamber and a lower airchamber. This idea of ar ranging the water chamber above the air chamberis of considerable importance in the solution of the problem ofdesigning a successful concrete pressure cistern, and so far as I amaware the idea is new with me.

The pipe 14 passes through the partition 13 and in water and air tightrelation therewith. It may terminate at its lower end either immediatelyor at some distance beneath the partition, or it may extend almost to.the floor 11, but its upper end should be near the roof pipe 14: servesto transmit the air pressureto the surface of the water in the waterchamber.

Water from the pump is forced through the pipe 15 into the waterchamber, and as the water chamber fills up the air in both chambersbecomes compressed, the communicating pipe 1d resulting in anequalization of air pressures in the two chambers. The.

outlet end of the pipe 15, which may beat any level inthe water chamber,is. provided with anautomaticfioat valve for shutting off the'fiow ofwater when the water reaches a predetermined level in the. waterchamber. This level is preferably immediately beneath the upperend ofthe pipe 14, as otherwise the water might enter the pipe 14; and becarried down into the air chamber.

The pipe15 is of course provided with a check valve 16 to prevent. thewater-from flowing-back into the well. To avoid dam age; to thewindmill;v and the connections when the outlet of the pipe, 15 isautomatically closed by; the float valve, Iprovide a relief alve' 17 ofany suitable type, and

when I so desire I may make use of this relief valve to automaticallyshut 01f the windmill. One simple way of doing this is to suspend anempty pail fromthe shut off lover of the windmill with the mouth of thepail positioned where it will catch the overflow from the relief valve.The weight of the pail and'contentswillthen shut off the windmill. I mayhowever accomplish the same result with any. one of a great varietyofmechanical or electrical controls. These cxpedientsarc so well knownhowever that I do not deem it, necessary to illustrate them, in the.drawings.

Then my. cistern, is properly; set, up. and adjusted, the water from:the pump will tend-to maintain the requisite pressure, as there canbenoloss of air frpm the-cistern. In the event however that the airpressure should becometoo low, it-is asimplemattento .forcemorc air intothe cistern tl1rou 'h-the pipe 15; The water to bc used is. ofcoursewithdrawn through the pipe 18.

llcspite all precautions there is a tendency-forg a ccrtainquantity ofwater to enter the airchamber, but this quantity. will seldom. be.sufficient to interfere with the operation of my cistern. For removing.water which has entered the air chambenl have: provided an outletpipe19 with its lower end terminating just above. the floor of the; airchamber. The pipe l9 passes throughtheroof of the cistern andterminatesin a pit 20, the upper end being pro vided witlr a nozzle andavalve. To rid the air chambero'f water i-t'is only-necessary to openthevalveat the upper end of-the pipe 19 and toforce air through .the pipe..15 and into the-cistern.

hlanh-oles are; provided in the partition and roof respectively. Thesemanholes serve twopurposes, During the construction of the cistern it isnecessary that the builder do considerable work on the inside, themanholes'being necessary to give the builder access to theinter'ior.Also after the cistern has been in operation for a number of years itmay be necessary to enter the cistern for the purpose of repairing orrenewing portions of the pipe or for other purposes. The difficulties ofproviding an air tight and water tight closure for any kind of openingin a concrete wall are-very great, and so far as. I; am aware Iain thefirst to produce an effective. closure of that kind andat a cost whichwill make its installation feasible wlierevensuch a closure is needed.

I will now briefly describe my closure and the method of making it. Atthe. time of casting the partition and roof of mycistern, I embed a.rubber; ring 21 in A, the concrete. In some of; the ciste1'ns wh ichIha-ve con structed I used the material of which cushiontires for babycarriages, wheeled coasters, and bicycles are made; This I cut intostrips of suitable length and united the ends byv means of rubber orgutta percha cement, thus. making ringswhich are"so1newhat larger indiameterthai'i the opening which isto beclosed. This ring I securedtothe forms in sucha way that only a small portion, less than one fourth,would protrude from the, lower side of the concrete wall aftercasting.The closure p ropjer consists of a plate. 22 'having secured c'entrallythereto a rod23 which is'screw threaded at its upperend, Abovetheopening-I place aplate 24 or other suitable ab'ut 'nei'it with therod 93 passing, therethrough, and I then draw the. plate'22 tightlyag'ainstthe ring 21 by means of a nuton the screw threaded upper endofthe rod 23. This structure may however belvaried in several importantparticulars Instead of making the ring of rubber,

Imay employ'leather, asphalt, or any other mater al'wh'ich' is suitablefor the purpose.

The material must be appreciably compressible, and it shouldma-ke afairly close bond with the concrete. This bond should be as nearlyairtightaspossible, but even in the eventthat thjere should be a slightbreaking away of the ring from th'econcrete, the distance around the,transverse circumference of the ring is too great to permit the escapeof StilllClGIlbdll to make trouble in theoperation .ofth'e cistern,andthe natural tendency of the compressible material of the ring to fillup small gaps will entirely avoid the occurrence of trouble from thissource.

Concrete has been anexceedingly unsatisfactory material for containersfor holding air under pressure. Excessive pressures on the walls fofsuch containers are liable to result in-hair, cracks in the concrete antsuch hair cracksif permitted to develop in a cistern will entirelydestroy the usefulness of the pressure system because they cause a lossof air pressure through the loss of air, and incidentally they permitthewater to seep away through the cracks. Because of the vital importanceof this problem in a cistern of the kind which I describe, it isimportant that the various pressures in the cistern be considered. Inthe lower or air chamber of my cistern the air pressures are alldirected outwardly from the chamber. The pressures on the side walls andfloor of the air chamber are practically counterbalanced by the naturalresistance of the clay subsoil, and my experience has been that with afavorable subsoil that the plastered wall and fioor of the air chamberwill develop no hair cracks as the result of inter nal pressures. Theresistance of the soil likewise protects the side walls of the upper orwater chamber of my cistern. Air pressures on the top and bottom of thepartition 13 are equal, the only inequality in pressures being due tothe weight of the water in the upper chamber. This pressure is directeddownwardly on the lower portions of the wall 10 but the compression cannot develop the strains which result in cracks. The roof 12 is subjectedto air pressure on its lower side, but this pressure is only partlycounterbalanced by the pressure of the weight of the soil above it. Theinequality of pressures on the roof results in a tension on the upperportions of the wall 10, and unless pro-vision is made for counteractingthe upward pressure, cracks will develop in the wall of the waterchamber."

I will briefly explain how I protect the side walls of the water chamberagainst the upward pressure against the roof 12. At the time of castingthe partition and roof, I insert reinforcing rods or wires 25. After thesetting of the concrete and the removal of the forms I subject the rodsor wires to tension and then cover them with concrete plaster in orderto protect them from the action of water and air and to prevent theirrusting. In some instances I may apply the tension either beforeorduring the setting of the concrete. I may apply the tension to the rodsin any one of various ways, as for example by means of nuts and threadson the rods or by drawing together and tying the rods in pairs. Thespecific details of this feature and the reasons therefor will not bedwelt upon at length. in this application, since the structure is thesubject matter of my copending application, Serial Number 618733, filedFebruary 12th, 1923.

The dimensions of my cistern are susceptible of some variation, but theprinciples involved in its construction and operation depend very muchon dimensions having a small range of variation. The first consideration is of course the size, which should be amply large en ugh t meetthe normal water requirements of the average farm. The present pressuresystems will not do this. The cost of the steel tank of ample size isprohibitive. My problem has beenthe problem of so constructing thepressure cistern of ample size and ata reasonable costthat itsinstallation would be profitable on the great majority of farms.

By reducing the diameter and increasing the length of the cistern I verymaterially reduce the surface of cast concrete and increase the amountof surface of plastered concrete. This results in a very materialreduction in costs since it reduces the amount of farm work and since itrequires less cement. This latter is readily apparent from the fact thatthe plastered wall is only about three-fourths of an inch thick whilethe cast wall is from five to ten inches thick. The reduction of thediameter has another advantage in that the danger of cracking the sidewalls is correspondingly reduced. This is true because the burstingpressure of a cylindrical container of gas under pressure variesdirectly as the diameter. Still an other advantage is due to the factthat the upward pressure of the air on theunder surface of the roof 12varies directly as the square of the diameter of the roof. I find itadvantageous to construct the roof with a diameter not to exceed fivefeet three inches. With this diameter and an air pressure of twentypounds per square inch inside the chamber, the upward pressure on theroof is approximately sixty thousand. pounds, and since the weight ofthe roof is only about eighteen hundred pounds, there must be sufficientreinforcing material to properly anchor the roof to the partition. Thereinforcing material is costly, and since there is a considerablereduction in the amount needed with a reduction in the diameter of thecistern, it is obvious that the diameter should be decreased as much aspossible, the limit being determined only by the fact that it will benecessary for the operator or builder to do some of the constructionwork on the inside. If the diameter were reduced to three feet, theupward pressure on the roof would be so small that no reinforcing wouldbe needed.

In a cistern of five feet three inches diameter and having a depth offrom seven to seven and a half feet for the water chamber, there will bean ample supply of water for the average farm, with a liberal margin ofsafety to take care of the requirements for short periods when the Windis not sumciently strong to pump the water, or when as in the threshingseason the drain on the water supply is unusually heavy. In a cisternhaving these dimensions, I prefer to give the lower or air chamber adepth of from twelve and a haif te fourteen feet. The greater the volumeof compressed a r in Cir theair-chamber, the less variation there willbe atthefaucets. The pressure once established will be maintained by theinflow of water from the pump. No loss of air can occur except thatdissolved in the water under pressure, and this quantity will be sosmall that long periodscan elapse; before it becomes necessary torestore the air pressure by forcing additional air into the cistern.

The cost of construction is of course materially reduced by making bothchambers integral and in the same excavation. The equipment for makingthe excavation is in place and it is simply a continuation of the job toexcavate deep. enough to provide room for the-air and water chambers ina vertical plane. Likewise, the plastering of the walls is simplified bythe fact that there is only one continuous wall to be plastered.

Asbefore stated, the position of the water chamber above instead ofbelow the air chamber is ofvital importance, both in the constructionand in the successful operation of my cistern. It'is true that if thewater were stored in the bottom of the cistern the dividing partitioncould be dispensed with and that the cost of this partition could thusbe saved, but I believe the commercial failures of "many of the concretecisterns heretofore placed on the market are due to fundamentalprinciples which were .overlooked inthe designing of such cisterns. Inthe-consideration of concrete as a material for pressure cisterns, thechief factor to be considered is air pressure, because as before stated,internal pressures if excessive are apt to rupture the walls and toproduce hair cracks which release the air. In a cistern of thedimensions as I usually employ, a pressure of twenty pounds to thesquare inch is sufficient to lift the water in. the bottom of the waterchamber to tlie required height without causing any undue strain on thewalls of the cistern. The thin shell of concrete alone would notresistthis pressure. The soil wall however has an ample margin of safety inresisting a pressure of twenty pounds. The concrete wall serves very little more than as an airtight lining for the soil wall. If the waterhowever were stored at the bottom of the cistern, a pressure of aboutforty-five per cent greater would be requiredto lift the water atthebottom of the cistern to the same height above the ground- For somesoils this pressure is beyond the margin of safety, the only. solutionof the difiiculty being to strengthen the walls at-a cost which makesthe installation of the concrete cistern entirely out ofthe question onthe great majority of farms. The air pressure is however exerted in alldirections with the result that the lifting force against the under sideof thereof of the cistern is proportionately increased. This alsodemands construction which will resist the increased pressure, andwhether such constuction involves the use of suflicient additionalconcrete or sufiicient additional reinforcing or both, the additionalcost must result in the commercial failure of the cistern.

lVhile I have described the preferred form of my invention in veryspecific terms, I do not desire to restrict' myself to the exactstructure described, since it is obvious that nun'ierous changes couldbe made without departing from the spirit of my invention. This isespecially true'of the cistern itself, which I have described as beingmade of plastered walls and cast top and partition. In some instances itmay be desirable to cast the walls-also, or even to use other thancementitious materials in the construction of the cistern.

Having described my invention and its advantages, what I believe to benew and desire to secure by Letters Patent of the United tit-ates is 1.In a cistern. an underground cavity having an air tight lining on itssides and an air tight roof, a substantially horizontal partitiondividing the cavity into an upper water chamber anda lower air chamber,means for equalizing the air pressure air chamber and the upper part ofthe water chamber, and water-inlets and outlets for said water chamber,the arrangement being such that water cannot normally enter said loweror air chamber.

2. In a cistern, a cavity having an air tight lining on its sides andbottom and'having also an air tiglit'roof, a partition dividing thecavity into an upper water chamber and a lower air chamber, means forequalizingthe air pressure of said chambers, means for. conducting waterunder pressure into said water chamber, means for automatically stoppingthe inflow of water when the water reaches a predetermined level in saidwater chamber, and an outlet for the water whereby the water. from thewater chamber may be withdrawn.

3. In a cistern, anunderground cavity, a relatively thin shell ofconcrete secured to the earth walls and floor ofsaid cavity, a roof forsaid cavity, a partition dividing the cavityinto an upper and a lowerchamber, said lower chamber being designed to serve as acontainer of airunder pressure and said upper chamber being designed to serve as areservoir for the storage of water, means for equalizing. the internalpressures of the two chambers, means for conducting water under pressureinto said water chamber, and means for withdrawing the water from thebottom of said water chamber, the arrangement being such that watercannot normally enter said lower or air chamber.

at. In a cistern, an underground cavity, a relatively thin sheet ofconcrete secured to the'earth walls and to the floor of the cavity, aconcrete roof for the cavity, said roof being positioned beneath thesurface of the ground, a concrete partition intermediate the floor androof and dividing said cavity into an upper, Water storage reservoir anda lower air pressure chamber, an open pipe terminating in said airpressure chamber and above the water level of said water storagereservoir for equalizing the pressures of the two chambers, means foranchoring the roof to the partition, and means for conducting water intoand out of said water chamher.

5. In a cistern, an underground cavity, a

vessel Within said cavity, said vessel being enclosed on all sides, asubstantially horizontal partition dividing the interior of said vesselinto an upper water chamber and a lower air pressure .ehamber, means forequalizing the internal pressures of said two chambers, means forforcing out water which collects in the bottom of said air pressurechamber, and means for conducting Water into and out of said waterchamber.

In testimony whereof I affix my signature.

RICHARD n. DILL.

